Framework for object-oriented access to non-object-oriented datastores

ABSTRACT

A method, apparatus, and article of manufacture for accessing non-object-oriented data using object-oriented techniques. A computerized system in accordance with the principles of the present invention includes a &#34;bridge&#34; that interfaces between an application program and a non-object-oriented database management system to materialize data retrieved from the non-object-oriented database management system as objects that can be manipulated by the application program. The bridge includes a &#34;collection of object collections&#34; for modeling hierarchical structures, a datastore collection made up of one or more datastore persistent objects, and an instance manager. A datastore class definition tool generates class definitions for datastore persistent objects that encapsulate or wrapper the data retrieved from the non-object-oriented database management system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending and commonly-assignedpatent application Ser. No. 08/736,762, entitled "FRAMEWORK FOROBJECT-ORIENTED ACCESS TO NON-OBJECT-ORIENTED DATASTORES," filed on Oct.25, 1996, by Kenneth R. Blackman and Jack L. Howe III, now U.S. Pat. No.5,799,313, which application is incorporated by reference herein.

This application is related to the following copending andcommonly-assigned patent applications:

application Ser. No. 08/736,762, entitled "A METHOD FOR REPRESENTINGNON-OBJECT-ORIENTED DATASTORES USING A COLLECTION OF COLLECTIONS DATAMODEL," filed on same date herewith, by Kenneth R. Blackman and Jack L.Howe III U.S. Pat. No. 5,799,313;

application Ser. No. 08/738,294, entitled "A METHOD FOR THE INCREMENTALPRESENTATION OF NON-OBJECT-ORIENTED DATASTORES USING AN OBJECT-ORIENTEDQUERYABLE DATASTORE COLLECTION," filed on same date herewith, by KennethR. Blackman and Jack L. Howe III now U.S. Pat. No. 5,781,907;

application Ser. No. 08/738,104, entitled "A QUERY SYNTAX FOR ACCESSINGNON-RELATIONAL, NON-OBJECT-ORIENTED DATASTORES," filed on same dateherewith, by Kenneth R. Blackman and Jack L. Howe III now U.S. Pat. No.5,778,379;

application Ser. No. 08/738,082, entitled "A QUERY PARSER FOR ACCESSINGNON-RELATIONAL, NON-OBJECT-ORIENTED DATASTORES," filed on same dateherewith, by Kenneth R. Blackman and Jack L. Howe III now U.S. Pat. No.5,778,358;

application Ser. No. 08/738,330, entitled "A METHOD FOR USING ADATASTORE CURSOR FOR THE INCREMENTAL PRESENTATION OF QUERY RESULTS WHENTRAVERSING IMPLIED COLLECTIONS IN NON-OBJECT-ORIENTED DATASTORES," filedon same date herewith, by Kenneth R. Blackman and Jack L. Howe III nowU.S. Pat. No. 5,787,436

application Ser. No. 08/736,759, entitled "A METHOD FOR REPRESENTINGDATA FROM NON-RELATIONAL, NON-OBJECT-ORIENTED DATASTORES AS QUERYABLEDATASTORE PERSISTENT OBJECTS," filed on same date herewith, by KennethR. Blackman and Jack L. Howe III now U.S. Pat. No. 5,794,247;

application Ser. No. 08/736,764, entitled "A METHOD FOR ENCAPSULATINGDATA FROM NON-OBJECT-ORIENTED DATASTORES AS DATASTORE PERSISTENTOBJECTS," filed on same date herewith, by Kenneth R. Blackman and JackL. Howe III now U.S. Pat. No. 5,765,161;

application Ser. No. 08/738,103, entitled "A METHOD FOR USING QUERYABLEPERSISTENT IDENTIFIERS TO LOCATE DATA FOR DATASTORE PERSISTENT OBJECTSIN NON-OBJECT-ORIENTED DATASTORES," filed on same date herewith, byKenneth R. Blackman and Jack L. Howe III now U.S. Pat. No. 5,765,163;

application Ser. No. 08/736,983, entitled "A METHOD FOR INTERFACINGQUERYABLE DATASTORE PERSISTENT OBJECTS TO NON-RELATIONAL,NON-OBJECT-ORIENTED DATASTORES," filed on same date herewith, by KennethR. Blackman and Jack L. Howe III now U.S. Pat. No. 5,761,671;

application Ser. No. 08/736,952, entitled "A METHOD FOR MANAGINGQUERYABLE DATASTORE PERSISTENT OBJECTS AND QUERYABLE DATASTORECOLLECTIONS IN AN OBJECT-ORIENTED ENVIRONMENT," filed on same dateherewith, by Kenneth R. Blackman and Jack L. Howe III now U.S. Pat. No.5,765,162;

application Ser. No. 08/736,765, entitled "A METHOD FOR CATALOGINGDATASTORE CHARACTERISTICS AND DEFINING AND GENERATING DATASTOREPERSISTENT OBJECTS," filed on same date herewith, by Kenneth R. Blackmanand Jack L. Howe III now U.S. Pat. No. 5,737,597;

application Ser. No. 08/736,922, entitled "A METHOD FOR CAPTURING ANDCATALOGING DATASTORE CHARACTERISTICS TO DEFINE DATASTORE PERSISTENTOBJECTS," filed on same date herewith, by Kenneth R. Blackman and JackL. Howe III now U.S. Pat. No. 5,809,508;

application Ser. No. 08/738,102, entitled "A METHOD FOR CAPTURING ANDCATALOGING SPECIFICATIONS FOR DATASTORE PERSISTENT CLASSES," filed onsame date herewith, by Kenneth R. Blackman and Jack L. Howe III now U.S.Pat. No. 5,737,598;

application Ser. No. 08/738,761, entitled "A METHOD FOR CAPTURING ANDCATALOGING PROGRAM CHARACTERISTICS FOR THE USAGE OF DATASTORE PERSISTENTCLASSES," filed on same date herewith, by Kenneth R. Blackman and JackL. Howe III; and

application Ser. No. 08/738,105, entitled "A METHOD FOR USING ANON-OBJECT-ORIENTED DATASTORE AS A GENERIC PERSISTENT DATASTORE FORPERSISTENT OBJECTS," filed on same date herewith, by Kenneth R. Blackmanand Jack L. Howe III now U.S. Pat. No. 5,809,509;

all of which applications are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to computerized methods foraccessing datastores, and in particular, to a computerizedobject-oriented method for accessing non-object-oriented datastores.

2. Description of Related Art

It is well known in the art to use database management systems, such asIBM's IMS™ (Information Management System) database management system,to manage computerized datastores. Indeed, IMS™ has been used fordecades and remains in use today. Currently, there is a need to accesssuch "legacy" datastores using application programs developed byobject-oriented programming systems (OOPS). However, there are few toolsavailable to assist OOPS programmers.

One method for allowing object-oriented application programs to accessdata in an IMS™ datastore is through transaction wrappering, implementedin such products such as IBM's VisualAge™ IMS Connection. Transactionwrappering creates a class having methods that retrieve data from theIMS™ datastore, create an object embodying the retrieved data, andmanipulate the object in an object-oriented application program. Theproblem with this approach is that each object-oriented applicationrequires substantial additional coding, both object-oriented andnon-object-oriented, before it is able to access the data in the IMS™datastore.

Another approach to accessing data in a non-relational,non-object-oriented datastore is to translate the non-relationaldatastore to a relational datastore, and use existing object-orientedprogramming techniques developed for relational datastores to access thedata therein. The problem with this approach is that non-relationaldata, such as the hierarchical data found in an IMS™ datastore, does notmap well to a relational datastore.

Thus, there is a need in the art for improved techniques for bridgingbetween non-object-oriented datastores and object-oriented applicationprograms.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesa method, apparatus, and article of manufacture for object-orientedaccess to non-object oriented datastores. A computerized system inaccordance with the principles of the present invention provides a"bridge" that interfaces between an application program and anon-object-oriented database management system to materialize dataretrieved from the non-object-oriented database management system asobjects that can be manipulated by the application program. The bridgeincludes a "collection of object collections" for modeling hierarchicalstructures, a datastore collection made up of one or more datastorepersistent objects, and an instance manager. A datastore classdefinition tool generates the class definitions for datastore persistentobjects that encapsulate or wrapper the data retrieved from thenon-object-oriented database management system.

Various advantages and features of novelty which characterize theinvention are pointed out with particularity in the claims annexedhereto and form a part hereof. However, for a better understanding ofthe invention, its advantages, and the objects obtained by its use,reference should be made to the drawings which form a further parthereof, and to accompanying descriptive matter, in which there isillustrated and described specific examples of an apparatus inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 is a block diagram illustrating an exemplary hardware environmentused to implement the preferred embodiment of the present invention;

FIG. 2 is a block diagram illustrating a collection of collections datamodel according to the present invention;

FIG. 3 is a block diagram illustrating an exemplary datastore collectionof the bridge according to the present invention;

FIG. 4 is a block diagram illustrating the operation of the bridgeaccording to the present invention;

FIG. 5 is a block diagram illustrating the operation of the instancemanager of the bridge according to the present invention; and

FIG. 6 is a block diagram illustrating the operation of the classdefiner tool according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description of the preferred embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration a specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Overview

The present invention provides object-oriented access to data in anon-object-oriented datastore. A computerized system in accordance withthe principles of the present invention provides a "bridge" thatinterfaces between an application program and a non-object-orienteddatabase management system to materialize data retrieved from thenon-object-oriented database management system as objects that can bemanipulated by the application program. The bridge includes a"collection of object collections" for modeling hierarchical structures,a datastore collection made up of one or more datastore persistentobjects, and an instance manager. A datastore class definition toolgenerates class definitions for datastore persistent objects thatencapsulate or wrapper the data retrieved from the non-object-orienteddatabase management system.

Hardware Environment

FIG. 1 is a block diagram illustrating an exemplary hardware environmentused to implement the preferred embodiment of the invention. Aworkstation or terminal 100 communicates with a server computer 102.Both the workstation 100 and the server computer 102 are typicallycomprised of one or more processors, random access memory (RAM),read-only memory (ROM), and other components such as data storagedevices and data communications devices.

The workstation 100 executes one or more computer programs 104 operatingunder the control of an operating system 106, such as the MVS™, VM™,AIX™, OS/2™, Windows™, Macintosh™, AS/400™, or UNIX™ operating systems.These computer programs 104 transmit commands to the server computer 102for performing various functions and receive data from the servercomputer 102 in response to the commands.

The server computer 102 also operates under the control of an operatingsystem 108, such as the MVS™, VM™, AIX™, OS/2™, Windows™, Macintosh™,AS/400198 , or UNIX™ operating systems. The server computer 102 executesone or more computer programs 110 and 112 under the control of theoperating system 108. These computer programs 110 and 112 receivecommands from the workstation 100 for performing various functions andtransmit data to the workstations 100 in response to the commands.

The server computer 102 manages one or more external databases ordatastores 114 stored on one or more data storage devices 116 (such as afixed or hard disk drive, a floppy disk drive, a CD-ROM drive, a tapedrive, or other device). In the preferred embodiment, the externaldatastore 114 comprises an IMS™ datastore managed by an IMS™ databasemanagement system (DBMS) product offered by IBM Corporation. Thoseskilled in the art will recognize, however, that the present inventionmay be applied to any datastore and associated database managementsystem.

The present invention is generally implemented using five majorcomponents executed by the workstation 100 and the server computer 102,i.e., object-oriented application program 104, workstation operatingsystem 106, server operating system 108, bridge 110, and datastoremanager (DSM) 112, wherein each of these components comprise one or morecomputer programs. The object-oriented application program 104 performsapplication functions; the workstation operating system 106 controls theoperation of the workstation 100; the server operating system 108controls the operation of the server computer 102; the bridge 110materializes data retrieved from the external database 114 as objects;and the datastore manager 112 controls access to the external database114.

Generally, these computer programs 104-112 are all tangibly embodied inor retrievable from a computer-readable medium, e.g., a data storagedevice or a data communications device. Moreover, the computer programsare all comprised of instructions which, when read and executed by theworkstation 100 and/or server computer 102, causes the workstation 100and/or server computer 102 to perform the steps necessary to implementand/or use the present invention.

Those skilled in the art will recognize that any combination of theabove components, or any number of different components, includingcomputer programs, peripherals, and other devices, may be used toimplement the present invention, so long as similar functions areperformed thereby.

Datastore Model

FIG. 2 is a block diagram illustrating the collection of collectionsdata model used in the present invention. Data retrieved from thenon-object-oriented external datastore 114 is modeled as a "collectionof object collections" in the bridge 110. Where the external data has asimple structure, each record is encapsulated as an object, whichbecomes a member of an object collection. Where the records arehierarchical in structure, that hierarchical structure is modeled bycreating object collections and then hierarchically connecting therelated object collections. Other complex logical records can be modeledas a hierarchy of object collections. A single collection of collectionsis materialized for each datastore, e.g., the object model of two flatfiles is a model having two collections of collections.

Block 200 represents the logical hierarchical structure of the data asstored in the external datastore 114, and block 202 represents thelogical "collection of object collections" structure created from thedata retrieved from the external datastore 114. The bridge 110translates the data between the differing formats and structures inblocks 200 and 202.

In the logical hierarchical structure of block 200, parent record A(204) has children records B (206) and C (208), and child record C (208)is also a parent of children records D (210) and E (212). There may alsobe multiple instances of parent record A (214 and 216).

Similarly, in the logical "collection of object collections" structureof block 202, parent object A (218) has children objects B (220) and C(222), and child object C (222) is also a parent of children objects D(224) and E (226). Further, there are multiple instances of parentobject A (228 and 230). Each of these objects is a datastore persistentobject (DPO) that encapsulates a logical unit of data, i.e., record,retrieved from the non-object-oriented datastore, and includes memberfunctions for manipulating the encapsulated data. Thus, the differencebetween blocks 200 and 202 is that each record A, B, or C in block 200is represented by a DPO in block 202, and the hierarchy in block 200 isrepresented by the collections of object collections in block 202.

Datastore Collection

The bridge 110 manages "datastore collections", which are the foundationof the "collections of object collections" data model. The members ofthe datastore collection are the DPOs. The datastore collection alsoincludes a query evaluator having a query syntax and a query parser, aqueryable datastore cursor, and an associated result collection with acursor. For complex queries, queries may be sub-divided. Results for thequeries are presented in user-specifiable increments, which permits thedelivery of large result collections while controlling use of memory.

FIG. 3 is a block diagram illustrating an exemplary datastore collection300 of the bridge 110 according to the present invention. The datastorecollection 300 includes a query evaluator 302 for receiving a query fromthe application program 104, wherein the query evaluator 302 comprises aquery syntax and a query parser. The query evaluator 302 parses thequery request in accordance with the query syntax and stores the parsedrequest in a parse table in a query object 304. A datastore cursor 306retrieves the parsed query from the query object 304 and provides theparsed query to an instance manager 308, which coordinates requests fromthe application program 104 with the datastore collection 300 and theexternal datastore 114. The instance manager 308 uses a schema mapper310 to interface with the datastore manager 112. The datastore manager112 retrieves data from the external datastore 114 on the externalstorage device 116 and returns the requested data to the schema mapper310. The schema mapper 310 translates common elements between therequested data retrieved from the external datastore 114 and a DPO 312,which results in the requested data being encapsulated in the DPO 312.The schema mapper 310 returns the DPO 312 through the instance manager308 to the datastore cursor 306 which stores the DPO 312 in the resultcollection 314. Generally, the result collection 314 comprises one ormore DPOs 316, 318, and 320.

The datastore cursor 306 populates the result collection 314 so that theapplication program 104 can incrementally access the query result.Because the number of data items or records requested by the query maybe large, the datastore cursor 306 only populates the result collection314 with a specified number of DPOs 316, 318, and 320 that correspond tothe query request. A pointer to the current DPOs 316, 318, or 320 ismaintained by the cursor 322, and the size of the result collection 314is determined by a size variable 324.

If the application program 104 needs to access more data items orrecords that satisfy the query, the datastore cursor 306 deletes one ormore of the DPOs 316, 318, and 320 from the result collection 314 andrequests the instance manager 308, through the schema mapper 310, toretrieve additional DPOs 312, up to the number indicated in the sizevariable 324, into the result collection 314.

In addition to populating a DPO 312 with data from the externaldatastore 114, the schema mapper 310 updates the external datastore 114with changed data from the DPO 312. The schema mapper 310 may add datato the external datastore 114 when a new DPO 312 is created, and theschema mapper 310 may delete corresponding data from the externaldatastore 114 when a existing DPO 312 is deleted.

The schema mapper 310 translates queries to specific instructions forthe datastore manager 112. Generally, these instructions comprise:SELECT, UPDATE, INSERT and DELETE, wherein the SELECT instructionretrieves data from the external datastore 114 via the datastore manager112 for a DPO 312; the UPDATE instruction, following a SELECT, saveschanged data from the DPO 312 into the external datastore 114 via thedatastore manager 112; the INSERT instruction saves new data from theDPO 312 into the external datastore 114 via the datastore manager 112;and the DELETE instruction deletes the DPO 312 and its correspondingdata from the external datastore 114 via the datastore manager 112.

Datastore Persistent Objects (DPOs)

The members, or elements, of the datastore collection 300 are queryableDPOs 316, 318, and 320 that encapsulate external data, i.e., recordsretrieved from the external datastore 114, with associated methods tomove data with data type integrity between the DPOs 316, 318, and 320,and the records of the external datastore 114. Thus, a DPO 316, 318, and320 makes non-object-oriented data accessible as "base class objects"that may be used or wrappered by other classes in an object-orientedprogramming system. Further, the data being encapsulated by the DPOs316, 318, and 320 may or may not be concurrently shared or updatedbetween object-oriented and non-object-oriented applications, dependingon the characteristics of the underlying datastore 114.

The bridge 110 thus comprises a queryable persistence implementationthat can be used to access data in non-object-oriented datastores 114.The bridge 110 provides a datastore persistent object class to wrapperdata retrieved from the external datastore 114, a queryable persistentidentifier (PID) used to specify information used to locate the data inthe external datastore 114 needed to populate the particular DPO 312,and a schema mapper class used to obtain the required data from theexternal datastore 114 and translate or transfer it into the format ofthe particular DPO 312.

FIG. 4 is a block diagram illustrating the operation of the bridge 110according to the present invention. The application program 104 passes aquery request to the datastore collection 300. The datastore collection300 evaluates the query and passes control to the datastore cursor 306for processing. The datastore cursor 306 creates a DPO 312 and itsassociated PID 400. The PID 400 is used to specify the query informationneeded to locate the data in the external datastore 114.

The DPO 312 and PID 400 are passed to the instance manager 308 whorequests that the schema mapper 310 retrieve the data via the datastoremanager 112 for storing into the DPO 312. The schema mapper 310 looks atthe DPO 312 accompanying PID 400 which has information from the queryobject 304 for locating data. The schema mapper 310 provides theinput/output commands to the datastore manager 112 using informationfrom a subschema mapper 402 and program specification block (PSB) 404.The schema mapper 310 receives the located logical unit of data from thedatastore manager 112 and maps the located data into the DPO 312,thereby "wrappering" the logical unit of data. Upon completion of theoperation, the DPO 312 then encapsulates the data retrieved by theschema mapper 310.

Instance Manager

FIG. 5 is a block diagram illustrating the operation of the instancemanager 308 according to the present invention.

In the run-time environment, the datastore collections 300 and DPOs 316,318, and 320 are managed (e.g., created, tracked, materialized,destroyed, and garbage collected) by the instance manager 308. Theinstance manager 308 also participates in the unit-of-work between theapplication program 104 being served and the external datastore 114.

Although the interface to the application program 104 remains constant,the level of service provided by the instance manager 308 will varyaccording to the characteristics of the external datastore 114. Theinstance manager 308 will exploit the capabilities of the externaldatastore 114 and the datastore manager 112 wherever possible, e.g.,with regard to query functions, concurrency, security, etc.

The instance manager 308 uses service classes to isolate some of itsfunctions, system services object (SSO) 500, interface object services(IOS) 502, and subschema mapper 402. The SSO 500 serves as a "factory"for creating DPO 312 and datastore collections 300 requested by queryobjects 304. The SSO 500 further serves as a transaction manager for theunit-of-work.

The SSO 500 receives a unit-of-work request from the application program104. The SSO 500 creates a subschema mapper 402 and opens a PSB 404 forthe unit-of-work request. The SSO 500 interfaces to the datastoremanager 112 through the IOS 502. The IOS 502 opens and closes theconnection to the datastore manager 112.

Using the schema mapper 310, the instance manager 308 populates thedatastore collection 300 with DPOs 316, 318, and 320 that encapsulatedata retrieved from the external datastore 114 via the datastore manager112. The schema mapper 310 updates the external datastore 114 withchanged data from the DPOs 316, 318, and 320, and adds or deletes theassociated elements from the external datastore 114 when the DPOs 316,318, and 320 are added or deleted.

The SSO 500 propagates a request to complete a unit-of-work to theinstance manager 308, the datastore collection 300, the schema mapper310, and the DPOs 316, 318, and 320, so as to coordinate the requestswith the datastore manager 112 to maintain the integrity of the externaldatastore 114. Upon completion of the unit-of-work, the instance manager308 deletes the DPOs 316, 318 and 320, the datastore collection 300, andschema mapper 310, from the memory of the server computer 102.

Datastore Class Definition Tool (CDT)

To minimize the need for writing non-object-oriented code to access thenon-object-oriented datastore 114, the datastore persistent objectclasses and methods used in the present invention are generated by aDatastore Class Definition Tool (CDT). At run-time, the bridge 110instantiates datastore persistent objects for these classes and directsthe retrieval of data from the external datastore 114 into the datastorepersistent objects.

FIG. 6 is a block diagram illustrating the operation of the CDT 600according to the present invention. The CDT 600 executes under thecontrol of the operating system 106 on the workstation 100 and interactswith an operator via a Graphical User Interface (GUI) 602.

A define datastore specification function 604 of the CDT 600 capturesinformation from a database description and the record layout, andassociates them to one another to define a datastore specificationstored in a CDT datastore catalog 606. The database description includesinformation about the structure of the segments in the externaldatastore 114 and the record layouts include formatting information forthe records in the datastore 114. The database descriptions and recordlayouts accessed by the CDT 600 are typically located on the servercomputer 102.

The define datastore specification function 604 that associates thedatabase description with the record layout can either be doneautomatically by the CDT 600 or in response to a command from a DatabaseAdministrator (DBA). The resulting datastore specification contains therelevant information extracted from the database description and therecord layout, and links the database description and record layouttogether. The define datastore specification function 604 may furtherperform an augment function that captures additional information toassist in defining the datastore specification.

A define datastore persistent object specification function 608 of theCDT 600 uses the datastore specification in the CDT datastore catalog606 and DBA input to define a datastore persistent object specification,which is then stored in the CDT datastore catalog 606. The definedatastore persistent object specification function 608 may furtherperform an augment function that captures additional information toassist in defining the datastore persistent object specification and toconstrain the use of datastore persistent objects.

A generate datastore persistent object specification source codefunction 610 of the CDT 600 uses the datastore persistent objectspecification to generate source code for the datastore persistent classand its associated schema mapper class. The source code includes bothclass definitions and method implementations for the classes. The codegenerated by the CDT 600 is compiled, linked, and made available inexecutable form at run-time. The define program specification function612 of the CDT 600 captures characteristics of the object-orientedapplication program 104 to be executed on the workstation 100 as aprogram specification, which is stored in the CDT datastore catalog 606.The define program specification function 612 provides information aboutthe object-oriented application program 104 that is useful in generatingsubschema mapper class definition and method source code and PSB sourcecode. The define program specification function 612 of the CDT 600 mayfurther perform an augment function that captures additional informationto assist in defining the program specification.

The generate program specification source code function 614 of the CDT600 generates source code for PSBs and paired subschema mapper classdefinitions and methods. The code generated by the CDT 600 is compiled,linked, and made available in executable form at run-time.

Conclusion

This concludes the description of the preferred embodiment of theinvention. The following paragraphs describe some alternative methods ofaccomplishing the same objects.

In alternative embodiments of the present invention, other types andconfigurations of computers could be used. For example, the inventionneed not be restricted to client-server configurations. In addition,mainframes, minicomputers, or personal computers, could be used with thepresent invention.

In alternative embodiments of the present invention, other types andconfigurations of computer programs could be used. For example, theinvention need not be restricted to client-server configurations.

In alternative embodiments of the present invention, other databasemanagement systems could be used. For example, the invention need not berestricted to IMS™ database management systems. In addition, the presentinvention could be used to model other types of information.

In summary, the present invention discloses a method, apparatus, andarticle of manufacture for accessing non-object-oriented data usingobject-oriented techniques. A computerized system in accordance with theprinciples of the present invention includes a "bridge" that interfacesbetween an application program and a non-object-oriented databasemanagement system to materialize data retrieved from thenon-object-oriented database management system as objects that can bemanipulated by the application program. The bridge includes a"collection of object collections" for modeling hierarchical structures,a datastore collection made up of one or more datastore persistentobjects, and an instance manager. A datastore class definition toolgenerates class definitions for datastore persistent objects thatencapsulate or wrapper the data retrieved from the non-object-orienteddatabase management system.

The foregoing description of the preferred embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not by this detailed description, but rather by theclaims appended hereto.

What is claimed is:
 1. A computerized data retrieval apparatus, comprising:a bridge program, executed by a computer, that interfaces between an application program and a non-object-oriented datastore to materialize data retrieved from the non-object-oriented datastore in response to one or more query requests from the application program as one or more objects that can be accessed by the application program.
 2. The computerized data retrieval apparatus of claim 1, wherein the objects comprise datastore persistent objects.
 3. The computerized data retrieval apparatus of claim 1, wherein each logical unit of the retrieved data is encapsulated as an object.
 4. The computerized data retrieval apparatus of claim 1, wherein each object includes member functions for manipulating the encapsulated data.
 5. The computerized data retrieval apparatus of claim 1, wherein each object includes one or more associated methods to move the retrieved data with data type integrity between the object and the non-object-oriented datastore.
 6. The computerized data retrieval apparatus of claim 1, wherein the retrieved data encapsulated by each of the objects is concurrently shared between object-oriented and non-object-oriented application programs.
 7. The computerized data retrieval apparatus of claim 1, wherein the objects are base class objects that are used by other class definitions in an object-oriented programming system.
 8. The computerized data retrieval apparatus of claim 1, wherein the bridge program models hierarchical structures represented by the retrieved data as one or more collections of objects.
 9. The computerized data retrieval apparatus of claim 1, wherein a plurality of object collections are linked together as a hierarchical structure.
 10. The computerized data retrieval apparatus of claim 1, wherein results for the query requests are presented in increments to permit delivery of large collections while controlling use of memory in the computer.
 11. The computerized data retrieval apparatus of claim 1, wherein the objects are grouped into one or more collections and each of the collections includes a query evaluator having a query syntax, a query parser, and a queryable datastore cursor.
 12. The computerized data retrieval apparatus of claim 11, wherein the query parser parses the query request in accordance with the query syntax.
 13. The computerized data retrieval apparatus of claim 12, wherein the queryable datastore cursor provides the parsed query to an instance manager, which coordinates the query request between the collection and the non-object-oriented datastore.
 14. The computerized data retrieval apparatus of claim 13, wherein the instance manager uses a schema mapper to interface with the non-object-oriented datastore.
 15. The computerized data retrieval apparatus of claim 14, wherein a datastore manager retrieves the data from the non-object-oriented datastore and returns the retrieved data to the schema mapper.
 16. The computerized data retrieval apparatus of claim 14, wherein the schema mapper translates common elements between the retrieved data from the non-object-oriented datastore and an object, which results in the retrieved data being encapsulated in the object.
 17. The computerized data retrieval apparatus of claim 14, wherein the schema mapper returns the object through the instance manager to the queryable datastore cursor which stores the object in the collection.
 18. The computerized data retrieval apparatus of claim 14, wherein the schema mapper updates the non-object-oriented datastore with changed data from the objects.
 19. The computerized data retrieval apparatus of claim 14, wherein the schema mapper adds data to the non-object-oriented datastore when a new object is created.
 20. The computerized data retrieval apparatus of claim 14, wherein the schema mapper deletes corresponding data from the non-object-oriented datastore when an existing object is deleted.
 21. The computerized data retrieval apparatus of claim 14, wherein the schema mapper translates query requests to specific instructions for the non-object-oriented datastore.
 22. The computerized data retrieval apparatus of claim 11, wherein the queryable datastore cursor populates the collection so that the application program can incrementally access the query results.
 23. The computerized data retrieval apparatus of claim 11, wherein the queryable datastore cursor only populates the collection with a specified number of objects that correspond to the query request.
 24. The computerized data retrieval apparatus of claim 11, wherein a pointer to the current objects is maintained by the queryable datastore cursor.
 25. The computerized data retrieval apparatus of claim 1, further comprising a datastore class definition tool, executed by a computer, for generating class definitions for the objects that encapsulate the data retrieved from the non-object-oriented datastore.
 26. A computerized method of data retrieval, comprising the steps of:retrieving data from a non-object-oriented datastore in response to one or more query requests from an application program; and materializing the retrieved data as one or more objects that can be accessed by the application program.
 27. A program storage medium, readable by a computer, tangibly embodying one or more instructions executable by the computer to perform a method of data retrieval, the method comprising the steps of:retrieving data from a non-object-oriented datastore in response to one or more query requests from an application program; and materializing the retrieved data as one or more objects that can be accessed by the application program.
 28. A computerized method of data retrieval, comprising the steps of:receiving a query request from an application program at a datastore collection; evaluating the query request at the datastore collection and passing control to a datastore cursor for processing of the evaluated query request; creating an object and associated identifier at the datastore cursor, wherein the identifier specifies information needed to locate the data in the non-object-oriented datastore; passing the object and identifier to an instance manager, wherein the instance manager requests that a schema mapper retrieve the data via a non-object-oriented datastore for storing into the object; providing commands to the datastore manager from the instance manager using the identifier; and receiving the retrieved data at the schema mapper and mapping the retrieved data into the object, thereby wrappering the retrieved data.
 29. A computerized data retrieval apparatus, comprising:a bridge program, executed by a computer, for receiving a query request from an application program at a datastore collection, for evaluating the query request at the datastore collection and passing control to a datastore cursor for processing of the evaluated query request, for creating an object and associated identifier at the datastore cursor, wherein the identifier specifies information needed to locate the data in the non-object-oriented datastore, for passing the object and identifier to an instance manager, wherein the instance manager requests that a schema mapper retrieve the data via a non-object-oriented datastore for storing into the object, for providing commands to the datastore manager from the instance manager using the identifier, and for receiving the retrieved data at the schema mapper and mapping the retrieved data into the object, thereby wrappering the retrieved data.
 30. A program storage medium, readable by a computer, tangibly embodying one or more instructions executable by the computer to perform a method of data retrieval, the method comprising the steps of:receiving a query request from an application program at a datastore collection; evaluating the query request at the datastore collection and passing control to a datastore cursor for processing of the evaluated query request; creating an object and associated identifier at the datastore cursor, wherein the identifier specifies information needed to locate the data in the non-object-oriented datastore; passing the object and identifier to an instance manager, wherein the instance manager requests that a schema mapper retrieve the data via a non-object-oriented datastore for storing into the object; providing commands to the datastore manager from the instance manager using the identifier; and receiving the retrieved data at the schema mapper and mapping the retrieved data into the object, thereby wrappering the retrieved data. 